Abstract
Furniture such as desks and other items are provided with sound absorbing features consisting of micro-perforations extending through structures having vertical surfaces. The micro-perforations are formed using a LASER cutting tool or a punch and are either cylindrical or frustoconical. The micro-perforations are formed in drawer facings, doors, support structures, and free-standing objects and storage devices having vertical surfaces. The micro-perforations have diameters in the range of 0.20 to 0.70 mm. The micro-perforations have been found to increase sound absorption of a desk by as much as 4 Sabins within the frequency range of 100 to 5,000 Hz. Structural panels consisting of front and rear micro-perforated panels surrounding a porous central core may be employed in such furniture.
Claims
1. An article of furniture in combination with a room in which said article of furniture is located, said article of furniture comprising: a) structures having vertical and horizontal surfaces; h) at least one of said structures consisting of at least one panel having (i) a front veneer with micro-perforations extending completely therethrough, (ii) a sound porous core behind said front veneer, and (iii) a rear veneer behind said sound porous core and having micro-perforations extending therethrough, said micro-perforations of said front veneer acoustically connected to porous aspects of said sound porous core; c) said micro-perforations having an average diameter within a range of from 0.25 to less than 0.45 mm; d) said article of furniture being located within said room whereby sounds within said room defined by soundwaves impinging upon said at least one panel are attenuated when they enter said micro-perforations; and e) whereby as compared to another article of furniture devoid of said at least one panel, said article of furniture including said at least one panel exhibiting enhanced sound absorption measured by increased Sabin values and reducing sound reverberation time, thereby enhancing ability of occupants in said room to clearly hear spoken words and to communicate.
2. The article of furniture of claim 1, wherein said micro-perforations are generally cylindrical.
3. The article of furniture of claim 1, wherein said micro-perforations are generally frustoconical.
4. The article of furniture of claim 3, wherein said micro-perforations have a larger diameter at a front surface of a structure having said micro-perforations.
5. The article of furniture of claim 1, wherein said micro-perforations extend into said structures having vertical surfaces.
6. The article of furniture of claim 1, comprising a desk.
7. The article of furniture of claim 6, wherein said desk has a horizontal structure having a horizontal flat surface.
8. The article of furniture of claim 6, wherein said desk includes at least one storage drawer having a front vertical closure structure having a flat front surface, said front vertical closure structure having a plurality of micro-perforations extending therethrough.
9. The article of furniture of claim 6, wherein said desk includes a storage compartment with a front opening closed by a vertical door having a flat front surface, said door having a plurality of micro-perforations extending therethrough.
10. The article of furniture of claim 7, wherein said horizontal structure is supported by a wide vertical leg with micro-perforations extending therethrough.
11. The article of furniture of claim 9, wherein said vertical door is pivotable about vertically disposed hinges.
12. The article of furniture of claim 9, wherein said storage compartment comprises a plurality of storage compartments, each closed by a door having a vertical surface, each door having a plurality of micro-perforations extending therethrough.
13. The article of furniture of claim 1, wherein said micro-perforations increase sound absorption of said article of furniture by up to 4 Sabins within a range of sound frequencies of 100 Hz to 5,000 Hz.
14. The article of furniture of claim 12, wherein said micro-perforations are generally cylindrical.
15. The article of furniture of claim 12, wherein said micro-perforations are generally frustoconical.
16. The article of furniture of claim 15, wherein said micro-perforations have a larger diameter at a front surface of a structure having said micro-perforations.
17. A sound absorbing desk in combination with a room in which said desk is located, said desk comprising: a) structures having vertical and horizontal surfaces, said horizontal surfaces including a writing surface; b) at least one of said structures consisting of at least one panel having (i) a front veneer with micro-perforations extending completely through vertical surfaces thereof, (ii) a sound porous core behind said front veneer, and (iii) a rear veneer behind said sound porous core and having micro-perforations extending therethrough, said micro-perforations of said front veneer acoustically connected to porous aspects of said sound porous core; c) said structures with vertical surfaces chosen from the group consisting of one or more of a door, a drawer front, and a support leg; d) said micro-perforations having an average diameter within a range of from 0.25 to less than 0.45 mm; e) said desk being located within said room whereby sounds within said room defined by soundwaves impinging upon said at least one panel are attenuated when they enter said micro-perforations; and f) whereby as compared to another article of furniture devoid of said at least one panel, said desk including said at least one panel exhibiting enhanced sound absorption measured by increased Sabin values and reducing sound reverberation time, thereby enhancing ability of occupants in said room to clearly hear spoken words and to communicate.
18. The desk of claim 17, wherein said micro-perforations are chosen from the group consisting of generally cylindrical and frustoconical.
19. The desk of claim 17, wherein said desk includes at least one storage drawer having a front vertical closure structure having a flat front surface, said front vertical closure structure having a plurality of micro-perforations extending therethrough.
20. The desk of claim 17, wherein said micro-perforations increase sound absorption of said desk by up to 4 Sabins within a range of sound frequencies of 100 Hz to 5,000 Hz.
21. (canceled)
22. The combination of claim 17, wherein said core is porous by virtue of a plurality of holes therethrough having diameters greater than 1 mm.
23. (canceled)
24. (canceled)
25. The combination of claim 17, wherein said core is porous by virtue of a plurality of slots therethrough.
26. The combination of claim 25, wherein said slots are parallel.
27. The combination of claim 1, chosen from the group consisting of a storage device, a desk, and a free-standing object.
28. The combination of claim 27, wherein said storage device has a plurality of cubicles defined by walls forming a rectangle.
29. The combination of claim 27, wherein said free-standing object is rectangular cubic with vertical walls having micro-perforations.
30. The combination of claim 27, wherein said free-standing object includes angled support walls with micro-perforations.
31. A structure for use in being incorporated into an article of furniture, comprising: a) a front veneer with a plurality of micro-perforations therethrough; b) a sound porous central core; and c) a rear veneer with a plurality of micro-perforations therethrough, said micro-perforations of said front veneer acoustically connected to porous aspects of said sound porous core; d) said micro-perforations in said front and rear veneers having diameters within the range of from 0.25 to less than 0.45 mm; e) said structure, when incorporated into an article of furniture and located in a room absorbing sound waves in said room and reducing sound reverberation time, thereby enhancing ability of occupants in said room to clearly hear spoken words and to communicate.
32. The structure of claim 31, wherein said central core is porous by virtue of a plurality of holes therethrough having diameters greater than 1 mm.
33. (canceled)
34. The structure of claim 31, wherein said central core is porous by virtue of a plurality of slots therethrough.
35. The structure of claim 31, oriented vertically in said article of furniture.
36. The structure of claim 31, oriented at an angle with respect to a vertical orientation.
37. The structure of claim 31, wherein said article of furniture is chosen from the group consisting of a storage device, a desk, and a free-standing object.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1 shows a traditional Helmholtz absorber with perforations having diameters greater than 1 mm.
[0033] FIG. 2 shows an example of a prior art office furniture integrated desk assembly.
[0034] FIG. 3 shows an acoustical furniture façade in an impedance tube used to test acoustical characteristics.
[0035] FIG. 4 shows three layers of structures in accordance with the teachings of the present invention incorporated into furniture.
[0036] FIG. 5 shows front, side, and cross-sectional views of a cabinet door made in accordance with the teachings of the present invention.
[0037] FIG. 6 shows front and cross-sectional views of a drawer front made in accordance with the teachings of the present invention.
[0038] FIG. 7 shows an integrated desk assembly similar to that which is shown in FIG. 2 but with vertical surfaces from the assembly of FIG. 2 replaced with micro-perforated structures in accordance with the teachings of the present invention.
[0039] FIG. 8 shows a detailed view of a micro-perforated absorber in which the perforations have diameters in the range of 0.25 to 0.65 mm.
[0040] FIG. 9 shows graphs of impedance and absorption versus frequency in Hz.
[0041] FIG. 10 shows a graph of the level of Sabins versus frequency comparing prior art furniture with furniture manufactured in accordance with the teachings of the present invention.
[0042] FIG. 11 shows a graph of reverberation time versus frequency in Hz comparing prior art furniture with furniture in accordance with the teachings of the present invention.
[0043] FIG. 12 shows a storage device including storage cubicles as well as drawers.
[0044] FIG. 13 shows a free-standing storage device having a plurality of openings providing volumes where objects can be stored and displayed.
[0045] FIG. 14 shows a wall-mounted storage device having a plurality of openings providing volumes where objects can be stored and displayed.
[0046] FIG. 15 shows a free-standing rectangular cubic object including vertical surfaces that may be improved with micro-perforations.
[0047] FIG. 16 shows a free-standing object having angled surfaces that may be improved with micro-perforations.
[0048] FIG. 17 shows a free-standing object having angled surfaces that may be improved with micro-perforations.
[0049] FIG. 18 shows an exploded perspective view of a panel made up of a central core with openings therethrough surrounded by micro-perforated panels.
[0050] FIG. 19 shows a further example, an exploded perspective view of a panel made up of a central porous core surrounded by micro-perforated panels.
[0051] FIG. 20 shows a yet further example, an exploded perspective view in which the core has a series of parallel slots.
[0052] FIG. 21 shows a further example, an exploded perspective view in which the core has slots extending completely therethrough.
SPECIFIC DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0053] Traditional approaches to absorb low and mid frequencies have relied on Helmholtz resonators, as shown in FIG. 1. While effective, this approach utilizes relatively large perforations with diameters between 4-12 mm, which visually impact the surfaces treated, and also require porous material in the rear cavity. Microperforated panel (MPP) devices, described by Ma in the 1960s, are Helmholtz resonators with very small holes. They provide absorption through high viscous losses as air passes through the holes that are only a bit larger than the boundary layer which is a thin skin of air covering every surface. This inherent damping eliminates the need for fiberglass or other porous materials in the air cavity between the perforated sheet and any reflective surface behind it although such materials do enhance sound attenuation. From a technical standpoint, consider a simple absorber formed by a cavity with a covering sheet. The covering sheet could either be perforated to form a Helmholtz design or be solid but flexible to form a membrane absorber. The impedance is given below, including the mass term given in Equation 1 (jωm), the resistance (r.sub.m) and the impedance of the cavity as the last term. These are the acoustic mass and resistance, respectively, due to the perforated sheet or membrane. The surface impedance of the resonant system is given by
z.sub.s1=r.sub.m+j[ωm−ρc cot(kd)], {1)
where k=2π/λ is the wavenumber in air, d is the cavity depth; in is the acoustic mass per unit area of the panel, ω is the angular frequency, ρ is the density of air, and c is the speed of sound in air.
[0054] A full expression for the mass is given by
[00001]
[0055] The last term in the equation is due to the boundary layer effect, and ν=15×10−6 m2s−1 is the kinemetric viscosity of air. This last term is often not significant unless the hole size is small, say, submillimeter in diameter. δ is the end correction factor, which, to a first approximation, is usually taken as 0.85 and derived by considering the radiation impedance of a baffled piston. Hence, using micro-perforations between 0.20 and 0.70 mm, we do not require porous absorption in the cavity and the perforations are not visible at normal viewing distances. In FIGS. 5 and 6, Applicants illustrate a schematic view of the layers comprising the micro-perforated panel.
[0056] With reference to FIG. 5 a cabinet door is designated by the reference numeral 10 and in the example shown is rectangular. A side view in FIG. 5 of the cabinet door 10 shows the hinges 11 and 13. With regard to the detail portion of the figure, reference is also made to FIG. 4 for a better understanding that the facing 15 is micro-perforated, the core 17 has perforations greater than 1 mm in diameter and the back face 19 is also micro-perforated. FIG. 6 shows a drawer front 20 and the detail shows the front portion 21 as well as a core 23 similar to the core 17 shown in FIG. 4. If desired, a micro-perforated back face (not shown) may be provided. The right hand image in FIG. 6 shows a veneer with frustoconical micro-perforations formed by a laser drilling device.
[0057] FIG. 4 shows an image of the micro-perforated face, the perforated core, and the micro-perforated rear face forming the inventive structure. In FIG. 3, the micro-perforated facade is shown in an impedance tube with an empty rear cavity of 12 inches, to mimic the depth of a typical cabinet for testing purposes.
[0058] The complex impedance (top) and normal incidence absorption measured in an impedance tube with a cavity depth of 12 inches are shown in FIG. 9. The vertical line at 200 Hz marks the frequency at which the Reactance crosses zero, resulting in a maximum in the absorption coefficient, for this configuration. The impedance tube is typically used as an engineering guide, since a relatively small sample size can be used, and the complex impedance can be studied. Evaluation of the normalized Resistance informs whether the sample offers too little or too much resistance to air. When it is ideally equal to 1, the absorption is at a maximum. In FIG. 9, the Resistance is roughly 0.7 and hence the absorption is 0.9.
[0059] Once the micro-perforated panel is designed and tested in an impedance tube such as shown in FIG. 3, a complete system can be measured in a reverberation chamber, using a sample size of, for example, 120 sq. ft. A comparison of the random incidence absorption coefficient for the non-acoustical and the micro-perforated version (the present invention) are shown in FIG. 10. The data clearly show the broad bandwidth of the acoustical furniture. When a planar sample of known surface area is measured, the Equivalent Absorption Area can be divided by the surface area to yield the traditional absorption coefficient. In this case, the effective absorption is shown as the Equivalent Absorption Area (sometimes called Sabins). The higher the Sabins number, the greater the sound absorption. FIG. 10 shows the superior performance of the furniture illustrated in FIG. 7 as compared to that of FIG. 2. In particular, FIG. 10 shows that the FIG. 7 furniture increased sound absorption compared to that of the FIG. 2 furniture by up to 4-5 Sabins in the frequency range of 100 Hz to 5,000 Hz. The indication of sound absorption up to 4-5 Sabins is merely exemplary. It is possible to achieve sound absorption to greater levels. FIG. 11 is a graph of reverberation time versus frequency and shows a reduction in reverberation time resulting from addition of micro-perforations in the subject furniture.
[0060] FIG. 1 shows a prior art traditional Helmholtz absorber panel which incorporates perforations having a diameter greater than 1 mm. Such a panel requires the rear thereof to face an absorbing material such as fiberglass or other material. This is required where large perforations are employed because the perforations themselves only allow sound waves to gain access to the rear portion. This is to be contrasted with micro-perforations in the range of 0.20 to 0.70 mm in which the perforations themselves provide sound attenuation and there is no need to provide a sound absorbing material to the rear.
[0061] FIG. 2 shows a prior art desk assembly generally designated by the reference numeral 30 and having structures with vertical and horizontal surfaces, including a horizontal desk structure 31 and 33, a vertical cabinet door 35, additional vertical cabinet doors 37, 39, 41 and 43, an additional horizontal surface 45, additional drawers 47 and 49, a vertical support structure 51 having a vertical surface, and a storage area closed by doors 53 and 55. Cabinet doors and drawer fronts are optional.
[0062] With reference to FIG. 7, the desk assembly 30 of FIG. 2 is modified into the desk assembly 60 having structures with vertical and horizontal surfaces in which the doors and drawers with front vertical surfaces from FIG. 2 are replaced by doors and drawers with front vertical surfaces 65, 67, 69, 71, 73, 77, 79, 81 (a wide vertical support leg), 83 and 85 with micro-perforated structures such as shown in FIGS. 4, 5 and 6, including a micro-perforated front face, a core with larger perforations and, if desired, a back micro-perforated face. The horizontal flat surfaces 61, 63 and 75 are unchanged from the respective structures 31, 33 and 45 from FIG. 2. The door 65, for example, pivots about vertical hinges 66. The doors and drawers are optional but, where included, can be micro-perforated to enhance sound attenuation.
[0063] FIG. 8 shows a preferred pattern of micro-perforations on a surface. The perforations have a diameter of between 0.20 mm and 0.70 mm. While one pattern of micro-perforations is shown, any desired pattern of perforations is conceivable. Since the micro-perforations are so small, they are barely visible to the naked eye. As such, more aesthetically pleasing patterns of micro-perforations are not necessary.
[0064] FIG. 12 shows a storage device 120 that includes a plurality of storage cubicles 121 defined by rectangular walls as well as a plurality of drawers 122. The cubicles have rear surfaces 123 that may be provided with a pattern of micro-perforations. Similarly, the faces of the drawers 122 may be provided with micro-perforations along with the face 124 of the stand 125.
[0065] FIG. 13 shows a free-standing storage device 130 having a plurality of openings, for example, 131, 132, 133, 134, etc. This storage device is open to the rear. The side edges such as those designated by the reference numerals 135 and 136 may be provided with a pattern of micro-perforations.
[0066] FIG. 14 shows a wall-mounted storage device 140 with a plurality of openings 141 formed by wall structures, for example, 142, 143, etc. The forward facing edges of the wall structures may be provided with micro-perforations.
[0067] FIG. 15 shows a free-standing rectangular cubic object that may be placed within a room area and may be used as a seat or as a support for another object such as, for example, a planter (not shown). The object 150 shows vertical side surfaces, for example, 151 and 152, that may be provided with patterns of micro-perforations to help attenuate sound in the room where the object 150 is located.
[0068] FIG. 16 shows another free-standing object 160 that may be used as a seat or as a support for another object, for example, a planter (not shown), and that includes a top surface 161 and side surfaces, for example, 162, 163, 164 and 165. These side surfaces are angled but they are not horizontal. Rather, they have both horizontal and vertical components. As such, the side surfaces may be provided with patterns of micro-perforations which will assist in attenuating sound in a room area where the object 160 is placed.
[0069] FIG. 17 shows a further example of a free-standing object 170 having a flat top surface 171 that can be used as a seat or to support any desired object. The object 170 includes angled support walls 172, 173, 174 and others as shown. While these side walls are angled, they can still be provided with micro-perforations that can be helpful in attenuating sound within a room where the object is located.
[0070] FIG. 18 shows structures generally designated by the reference numeral 180 that are similar to those shown in FIG. 4. They include a front veneer 181 having a multiplicity of micro-perforations therethrough, a central core 182 with holes therethrough larger than 1 mm in diameter and a rear veneer 183 covered with a pattern of micro-perforations. The central core can be of any desired thickness, for example, ¼″ to 1¼″. The central core can be made porous to sound by any desired means, such as, for example, holes larger than 1 mm in diameter, fibrous structures, honeycombing, structurally porous, etc. Cores may be made from MDF (medium density fiberboard).
[0071] FIG. 19 shows an exploded view of a panel 190 made up of a central core 192 which is porous though not through the provision of holes formed therethrough and is surrounded by veneers 191 and 193 which correspond to the veneers 181 and 183 shown in FIG. 18.
[0072] FIG. 20 shows another example 200 with a core 202 surrounded by veneers 201 and 203 corresponding to the veneers 181 and 183 of FIG. 18. The core 202 includes a plurality of parallel grooves 204 which have been found to be helpful in attenuating sound.
[0073] FIG. 21 shows a further example 210 which has veneers 211 and 213 corresponding the veneers 181 and 183 of FIG. 18. The central core 212 has the provision of multiple slots 214 extending completely therethrough to facilitate transmission of any sound traveling through the veneer 211 to the veneer 213.
[0074] In the preferred embodiments of the present invention, micro-perforated structures are typically only employed on vertical surfaces. Horizontal surfaces are not as impinged by soundwaves and adding micro-perforations to those surfaces does not result in appreciable increase in sound attenuation. Where a horizontal surface is a desk top, micro-perforations might be problematic, since, for example, spilled liquids could enter the micro-perforations and leak into the area below. However, surfaces that are angled, having a vertical component, could, if desired, be provided with micro-perforated surfaces. However, non-functional horizontal surfaces, such as the cabinet tops, can be micro-perforated for additional sound absorption.
[0075] Materials from which the micro-perforated structures can be created comprise any materials that can be micro-perforated using a laser cutting tool or a punch press or drill. The micro-perforations are typically formed using a laser cutting tool that can be configured to create micro-perforations that are either cylindrical or frustoconical (see FIG. 6). Where frustoconical micro-perforations are formed, the smaller diameter is to the rear of the face and the larger diameter is at the front of the face. Alternatively, micro-perforations can be formed using a drill, a drill press, a punch press or any other device that can create small diameter holes within the range of 0.20 to 0.70 mm in a solid piece of material. Applicants note that use of a laser cutting tool enables creation of frustoconical micro-perforations. This is not possible when using a drill, a drill press or a punch press. Micro-perforated structures can be made of wood, synthetic wood, particle board, and metals such as aluminum, again, so long as the micro-perforations can be formed using a laser cutting tool.
[0076] In one preferred configuration, a panel can consist of a front facing wood veneer, a central MDF core having holes therethrough, and a rear facing wood veneer. An example of this configuration is shown in FIG. 4 with reference to reference numerals 15, 17 and 19. The holes in the core can exist due to the structure of the core being a honeycomb configuration, fibrous, structurally porous or a rigid piece through which large holes greater than 1 mm in diameter are formed.
[0077] As such, an invention has been disclosed in terms of preferred embodiments thereof which fulfill each and every one of the objects of the invention set forth hereinabove and provide new and useful furniture with acoustical treatments of great novelty and utility.
[0078] Various changes, modifications and alterations in the teachings of the present invention may be contemplated by those skilled in the art without departing from the intended spirit and scope thereof.
[0079] As such, it is intended that the present invention only be limited by the terms of the appended claims.
